r32] 
82 
supplied from the summit level, tliis branch of the middle section majr 
be fed, in a great degree, by the streams wliich fall into it. 
Jfestern Branch of the Middle Section. 
This portion of the canal begins in Deep creek, five miles below 
the Base mark, and ends at the month of Bear creek. The lejiglk 
is 14 1 miles; and, like the former branch, it will receive from the 
summit level the waters required for it^> lockage. 
Hoy's Run, Steep Run, Sang Run, and Gap Rini,may be employed 
'^o feed it, and repair its losses; hut these strean^s have not been gang* 
ed. They may, nevertheless, offer sotae resources for reservoirs. 
iieav creek may also form a great j-eservoir, by damming its valley* 
and feeding the western section of the canal, but cannot fe^ed the west-. 
€rn branch of the middle section, from the differcnoe of t!>eir levels. 
Deep Creek is the only stream of any importance wljose waters 
may supply the losses of this branch from filtrations and evapora- 
tion; we should, therefore, C2an»ine accurately the means which it 
offers for this purpose. Its usual depth under the bri<lge is three 
feet; but in its freshets it rises to twelve feet, Fligh freshets gener- 
ally occur in this stream twice or thrice a-year, uiA last from three 
to four days: when the rains last so long, ir gives, during that time, 
from 400 to 5Q0 cubic feet a second. During the most unfavorable 
season it still has freshets, less considerabie, but which, nevertiieless, 
give it a mean discliarge about 100 cubic feet in a second, each time: 
these occur from six to eight times a year. Jn tlie dryest months it 
l^ives, under the bridge, irom 10 to 5| cubic feet a second: on the srtli 
August, 1824, it gave 5.12 cubic feet, which was the lowest quantity: 
we ever found. 
Supposing a dam erected across Deep Creek, at the head of its 
rapids, and five miles below the base mark, its basis would be 19? 
feet below that mark; its length would be 136| yards, and to raise 
its waters four feet above the base mark, its height should be 235 ^ect. 
This dam would raise the w aters of Deep Creek, so as to overflow an 
area of 948,924 square yards, from accurate surveys. The ])rism of 
this reservoir, comprised between its surface and a horizontal plane, 
run three feet below the base mark, would be seven feet high, and 
contain, in capacity, 2,214,156 cubic yards. In less thau three 
months of the rainy season, if we allow only 9 cubic feet, or one- 
third of a cubie yard a second, to tiie average supply of Deep Creek, 
this reservoir would be filled. It would be filled in less than five 
months in Summer, if the stream yielded at the rate of five cubic feet= 
Thus, every year, and for nine months of navigation, from the middle 
«f March to the middle of December, we may depend on a supply 
equal to twice the capacity of this basin, or 4,428,312 cubic yards. 
This is equivalent to 492,034 cubic yards a month, and supposes on- 
ly a mean supply of 5| cubic feet a second. This is the minimum 
of what Deep Creek can supply to repair the losses of the western 
lijranch of the middle section, from filtrations and evaporation. To 
